All three are disorders of the autonomic nervous system. That's the part of
the brain, spinal cord, and nerves that controls functions such as blood
pressure and bladder control; these functions are largely involuntary and below
our level of consciousness.

"Since other autonomic disorders like migraine and fainting seem to have
menstrual variations, we theorized that these conditions would have these
variations as well," says Thomas Chelimsky, MD, professor of neurology at Case
Western Reserve University in Cleveland.

IBS is characterized by abdominal pain, constipation, bloating, and diarrhea,
while fibromyalgia is characterized by pain throughout the body, along with
tender points. IC patients have pain in the bladder. All three conditions affect
women more than men. Stress and anxiety can exacerbate symptoms of all three,
Chelimsky tells WebMD.

For the study, 79 women with IBS, 77 women with fibromyalgia, and 129 women
with IC filled out a questionnaire asking about the severity of their symptoms
throughout the month.

A total of 25% of the IBS patients, 18% of the fibromyalgia patients, and 9%
of the IC patients reported worsening of symptoms during or before their period.

While not addressed by the study, Chelimsky believes fluctuations in hormone
levels may explain the findings.

"Estrogen is a pain preventative," Chelimsky says. Levels are at their lowest
right before menstruation and are still low while a woman has her period.

Additionally, 15% of women in the study reported worse pain at menopause,
another time estrogen levels drop. In a surprising finding that the researchers
could not explain, 37% of women said symptoms got worse at the time of their
first period.

Also unknown is why symptoms fluctuate with hormone levels in some women and
not others.

The findings of the poster presentation were reported here at the annual
meeting of the American Academy of Neurology.

Asked to comment on the findings, Nathan Wei, MD, clinical director of the
Arthritis and Osteoporosis Center of Maryland, says, "This study confirms the
clinical impression made by practitioners for many years -- that hormonal shifts
play a major role in symptom exacerbation."

Chelimsky says that other research shows that women with IBS, fibromyalgia,
and IC who are on estrogen-containing
birth control pills seem to have fewer
symptoms than other women with the conditions.